This application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2008-182861 filed in Japan on Jul. 14, 2008, the entire contents of which are herein incorporated by reference.
The present invention relates to a cleaning apparatus using a web sheet suitable for cleaning, for example, the fixing rollers of a fixing apparatus in an electrographic image-forming apparatus.
Recently, the processing speed of image-forming apparatuses has become higher. For example, the number of sheets that can be printed was 50 to 70 sheets/min (A4 landscape transport) several years ago, but the number has recently increased to 100 to 120 sheets/min (A4 landscape transport), and image-forming apparatuses are becoming used not only in the field of ordinary printing but also in the field of light printing.
In such image-forming apparatuses with higher processing speeds, smears on the fixing rollers in the fixing apparatus increase. The reason for this is that a larger number of sheets that can be printed leads to a larger total amount of toner that adheres to the fixing rollers. Conventionally, toner that has adhered to the fixing rollers is removed using blade cleaning, felt cleaning, or the like. However, in the case where smears on the fixing rollers increase, even if toner that has adhered to the fixing rollers is removed using this sort of method, the toner that has adhered once to a blade or felt may return to the fixing rollers, and, thus, cleaning durability is not sufficient for the period in which the fixing apparatus is used.
Thus, a web cleaning method is proposed as a conventional technique. In the web cleaning method, extraneous matters that have adhered to a fixing roller are removed by winding a web sheet made of a thin fabric onto a send-out roller, connecting an end of this web sheet to a take-up roller, sending out the web sheet from the send-out roller, taking up the web sheet onto the take-up roller and bringing the web sheet into contact with the fixing roller during the sending-out and taking-up operation (see JP 2006-106347A). If the length of the web sheet used is sufficient, the cleaning durability increases.
Here, in the technique described in JP 2006-106347A, rotational driving is controlled separately for the send-out roller and the take-up roller so that the amount of web sheet sent out and taken up is not excessive or insufficient, that is, so that the web sheet does not sag.
However, in the case where rotational driving is controlled separately for the send-out roller and the take-up roller in this manner, the driving mechanism and the control thereof become complex.
Furthermore, in the case where the driving mechanism is shared by the rollers (the send-out roller and the take-up roller) for the sake of simplicity, rotational driving cannot be controlled separately for the rollers, and, thus, the amount of web sheet sent out becomes different from the amount of web sheet taken up. Accordingly, in this case, a tension mechanism or the like for solving sagging of the web sheet has to be provided, and, thus, the structure becomes complex.
In this manner, conventionally, in order to solve sagging of a web sheet, the configuration of the apparatus has become complex.
The present invention was made in view of the above-described conventional problem, and it is an object thereof to provide a cleaning apparatus using a web sheet that can be effectively prevented from sagging with a simple configuration.